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Old 22 April 2013, 14:52   #1
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Testing different prop

This may be a silly question or complete heresy that will result in the destruction of my outboard and a collapse in the space-time continuum, but...

I'm off to try a coarser pitch prop at some point and it will (I assume) need a bit more oomph to keep it spinning when in gear at idle. Can I leave the mixture as it is but keep the idle revs up using the fast-idle lever when necessary, or does it need a proper re-tune for the new prop?
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Old 22 April 2013, 15:28   #2
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idle is idle. It will spin ever so slightly slower but that's just a function of the increase in pitch. You'll probably not notice the difference in use.
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Old 22 April 2013, 16:29   #3
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Seconded. It should be fine.

You might notice it's moving a bit faster at idle though. Watch the first time you try and come alongside.
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Old 22 April 2013, 17:15   #4
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You should play with prop pitch if boat is used heavily loaded or used with full stated passengers when at wot and that's with a tach to check achieved max rpm. Not at idle, idle rpm probably bit too low, adjust accordingly to factory specs.

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Old 23 April 2013, 02:40   #5
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Thanks All,

I'll give it a go.
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Old 23 April 2013, 04:14   #6
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Worst case, if it stalls, up the idle mix by 1/8 turn!

Alternatively if you have a super dooper modern EFI engine, it should take care of itself.....
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Old 23 April 2013, 06:33   #7
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and dont forget do not over rev the obm, you should have in your owners manual the optimum wide open throttle, do not excede it, and dont over rev in nutral either
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